1. Field of the Invention
The subject invention relates to single-handedly actuatable safety shields for needles to prevent accidental needle sticks.
2. Description of the Prior Art.
Accidental sticks with a used medical implement can transmit disease. Consequently many prior art hypodermic needles, blood collection needles, catheter needles and other sharply pointed medical implements are provided with a safety shield. The safety shield is intended to be placed over the sharply pointed tip of the medical implement immediately after removing the medical implement from the patient.
Some prior art safety shields define a rigid cap that can be telescoped in a proximal direction over the point of the needle cannula or other such medical implement. This re-shielding procedure requires the health care worker to hold the pointed medical implement in one hand and the shield in the other. The hands are then moved toward one another to effect the shielding. However, a misalignment during the shielding procedure could cause the accidental stick that the shield is intended to avoid. Additionally, this prior art shield presupposes that the health care worker will have two free hands to complete the shielding and that the shield will be readily available when the needle cannula or other such pointed implement is removed from the patient. In fact, many medial procedures require the health care worker to apply pressure to the penetration site immediately after the needle has been removed. Thus, the health care worker will apply pressure with one hand while manipulating the medical implement with the other hand. The unshielded needle may be placed on a nearby surface for shielding at a later time. This re-shielding easily can be overlooked as the health care worker attends to other needs of the patient. Additionally, the needle shield easily can be moved or misplaced between the initial unshielding and the intended reshielding.
Other prior art needle shields remain attached to the medical implement to avoid loss. The attachment may be a simple tether extending between the above described shield and the medical implement. Upon completion of a medical procedure, the health care worker will perform the two-handed telescoping of the tethered shield in a proximal direction over the point of the needle. This prior art shield avoids problems associated with loss. However, shielding cannot be completed until the health care worker has two free hands and the above-described potential exists for an accidental needle stick during the two-handed shielding procedure.
Still other prior art needle shields are constructed to enable single handed shielding. For example, some prior art shields are hingedly connected to the medical implement at or near the base of the needle. The shield is a rigid elongate structure, larger than the needle cannula, and open on one side to accept the needle. The shield is rotated away from the needle cannula while the medical implement is being used. The health care worker then uses one finger of the hand holding the medical implement to rotate the shield about the hinge and into a position where the needle cannula is partly surrounded. A variation of this basic design is disclosed in U.S. Pat. No. 5,242,417 which shows an over-center hinge connecting a shield to a medical implement. The over-center hinge is stably maintained in a rotational position that enables access to the needle cannula. After use, the shield is rotated toward the needle cannula. Initial rotational movement must overcome biasing forces exerted by the hinge. However, after sufficient rotational movement, the internal resiliency of the hinge urges the shield toward the needle cannula. The prior art hinged shields provide several efficiencies. However, the shield can sometimes interfere with convenient use of the medical implement and can block clear vision of the penetration site.
Prior art medical implements also include a needle shield that is telescoped over portions of the medical implement. These prior art shields are maintained in a proximal position over the medical implement prior to and during use. The shield then can be telescoped in a distal direction to safely surround the used needle cannula. Prior an shields of this type generally reduce the potential for accidental needle sticks during a shielding operation. However, these prior art shields can add significantly to the size, weight and cost of the medical implement. Additionally, most prior art shields of this type require two-handed activation of the shield. As noted above, two hands may not be available to the health care worker immediately after using the medical implement. Thus, the used medical implement may be kept in an unshielded condition. Prior art telescoping shields have been used with coil springs that are concentric with the needle cannula and that extend between the medical implement and the shield. A latch on the medical implement may keep the coil spring in a compressed condition prior to and during use of the medical implement. The latch may be released by a finger of the hand holding the medical implement to propel the shield distally and into a shielding disposition around to the needle cannula. Coil springs overcome the problem of two-handed activation. However, they further add to the size, weight and cost of the implement. Furthermore, the locks for holding further add to the complexity of the apparatus. These small plastic latches can possibly fail by either misfiring under the force of the spring or not releasing the spring at all.